Method for improving performance of highly stressed electrical insulating structures

ABSTRACT

Removing the electrical field from the internal volume of high-voltage structures; e.g., bushings, connectors, capacitors, and cables. The electrical field is removed from inherently weak regions of the interconnect, such as between the center conductor and the solid dielectric, and places it in the primary insulation. This is accomplished by providing a conductive surface on the inside surface of the principal solid dielectric insulator surrounding the center conductor and connects the center conductor to this conductive surface. The advantage of removing the electric fields from the weaker dielectric region to a stronger area improves reliability, increases component life and operating levels, reduces noise and losses, and allows for a smaller compact design. This electric field control approach is currently possible on many existing products at a modest cost. Several techniques are available to provide the level of electric field control needed. Choosing the optimum technique depends on material, size, and surface accessibility. The simplest deposition method uses a standard electroless plating technique, but other metalization techniques include vapor and energetic deposition, plasma spraying, conductive painting, and other controlled coating methods.

RELATED APPLICATION

[0001] This application relates to the U.S. Provisional Application No.60/051,518 filed Jul. 2,1997, and claims priority thereof.

[0002] The United States Government has rights in this inventionpursuant to Contract No. W-7405-ENG48 between the United StatesDepartment of Energy and the University of California for the operationof Lawrence Livermore National Laboratory.

BACKGROUND OF THE INVENTION

[0003] 1. Field of the Invention

[0004] The present invention relates generally to high-voltageinsulating structures, and more particularly to high-voltage bushings,connectors, and capacitors. The invention particularly relates to (i)high-performance feed-through bushings, (ii) high-performance coaxialconnectors, (iii) high-performance multilayer film capacitors that canbe operated with high-reliability, and (iv) methods for manufacturingthese high-performance components where electric field stresses areeliminated or sufficiently reduced in the so-called weak areas.

[0005] 2. Description of Related Art

[0006] Conventional high-voltage devices such as bushings, connectors,and capacitors use a combination of nonconductive and conductivematerials to construct desired high-voltage structures. Thenonconductive materials provide a dielectric barrier or insulatorbetween two electrodes of different electrical potential. A wide varietyof manufacturing techniques can be employed to construct insulators ofthe desired shape. Some of the processes that are most often usedinclude machining, molding, extrusion, casting, rolling, pressing,melting, painting, vapor deposition, plating, and other free-formingtechniques, such as dipping a conductor in a liquid dielectric orfilling with dielectric fluid, etc. The selection process must take intoaccount how one or both of the electrodes made from conductive materialwill be attached or adjoined to the insulator. The most importantfactors in producing reliable high-voltage structures are thought to bethe quality of the shape of the insulator and purity of the insulatormaterial. Ultimately, what limits the operating voltage of anyinsulation structure is the intrinsic electrical strength of thedielectric material. In practice, however, the operating levels fortypical designs are well below the intrinsic breakdown threshold of theinsulating material. The onset of electrical induced failure occurs atthe point in the material that cannot support the electric field stress.Electric field stress is defined as a function of voltage and geometricshape. Simply stated, the electric field across two infinite planeelectrodes is given by the difference in voltage of the two electrodesdivided by the separation distance. This is commonly referred to as theuniform or average field stress. Improvements in the operating levels ofa typical design are achieved with the use of impregnating materials. Anexcellent example of the use of impregnates is vacuum impregnated oilfilled capacitors. The air in fabricated capacitors is removed andpressure impregnated with evacuated dielectric oil. Also, an example mayinvolve cables with a coating on a center conductor. Another exampleinvolving a semiconductive coating on a highly stressed conductorindicates improvement in higher operating level of previous designs.Both techniques show a marked improvement over non-impregnated designs,but fall short of being able to operate at the intrinsic strength of thematerial.

[0007] The electric field stresses usually cause the most trouble in thecritical regions where dissimilar materials meet, particularly atso-called triple-point regions where a metal electrode and two differentdielectric materials are in direct proximity. At these locations,electric field stresses can become severely enhanced, increasing as muchas the ratio of the dielectric constants of the different materials, ormore, depending on the shapes of the materials. An excellent example ofthe control used to optimize this effect is described in copending U.S.application Ser. No. 09/034,797, filed Mar. 3, 1998, entitled“Ultra-Compact Marx Type High-Voltage Generator,” and assigned to thesame assignee. The essence of that invention provides contouredhigh-dielectric ceramic material and shaped electrodes to control fieldstress at the triple junction. In contrast, other fabrication techniquesmay or may not extend electrodes over the edge of straight dielectricsand reduce the operating level of the device. The reduction in operatinglevels is the result of reaching the intrinsic breakdown level of theweaker dielectric material at lower voltage.

[0008] Another problematic area where electric field stresses can leadto failure is in the placement or attachment of electrodes next to soliddielectric materials. Customarily, when the dielectric material ispressed or mechanically fitted between electrodes, there exists smallvoids that fill with some other material, typically the gas or liquid ofthe ambient environment in which the high-voltage structure resides.Usually, the material that fills the void has a lower electricalstrength than the solid dielectric material, and the electrical field inthis highly-stressed region may easily exceed the electrical strength ofthe void filling material. Moreover, for gas and many liquids having alower dielectric constant than the solid dielectric, there can be afield concentration in the void region that enhances the likelihood ofbreakdown in this weaker material.

[0009] The present invention overcomes these prior problems bymetalizing the surfaces of the solid dielectric materials wherevercontact is to be made with metal electrodes. Thus the electric fieldsare eliminated in the void regions, thereby preventing electricaldischarge (corona) activity that can lead to breakdown of the bulkdielectric material. The present invention is similar to thesolid-dielectric switch of the above-referenced application, wherefields across gaps are removed by metalizing dielectric surfaces. Animprovement of high-voltage bushings, connectors, and film-capacitorsbecomes a natural extension of the above-referenced application.

SUMMARY OF THE INVENTION

[0010] It is an object of the present invention to remove the electricfield from the weaker areas of the internal volume of high-voltageinterconnects:

[0011] A further object of the invention is to provide for removingelectric fields in weak areas of high-voltage bushings, connectors, andcables, such as transmission lines using wedge dielectric structuralsupports.

[0012] A further object of the invention is to provide a practical meansfor improving the performance of a wide variety of highly stressedinsulating structures.

[0013] A further object of the present invention is to provide a methodfor increasing the high-voltage performance of various bushings,connectors, and metal-film capacitors.

[0014] Another object of the invention is to provide a conductivesurface on the inside surface of the principal solid dielectricinsulator surrounding the center conductor and which connects the centerconductor to this conductive surface to eliminate electric fields.

[0015] Other objects and advantages of the present invention will becomeapparent from the following description and accompanying drawings.Basically, the invention involves removing the electric field from theweak areas of the internal volume of high-voltage interconnects.

[0016] The key attribute of the present invention is that it makes useof metalized regions over surfaces of dielectric material that will beattached to or in direct contact with adjoining metal electrodes, thuseliminating any electric field from the void region between the primarydielectric insulation and the adjacent metal electrodes where a weakerdielectric medium may exist.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which are incorporated into and form apart of the disclosure, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention.

[0018]FIG. 1A is a cross-sectional view of a generic cylindricalhigh-voltage bushing.

[0019]FIG. 1B is a view taken along the line 1B-1B of FIG. 1A.

[0020]FIG. 2A is a cross-sectional view of a typical bushing with anextended outer metalized surface.

[0021]FIG. 2B illustrates the equal-potential field gradient lines inthe typical bushing of FIG. 2A.

[0022]FIG. 3A is a cross-sectional view of an improved bushing made inaccordance with the invention.

[0023]FIG. 3B illustrates the equal-potential field gradient lines inthe improved bushing of FIG. 3A.

[0024]FIG. 4A is a cross sectional view of a further improved bushingwith a stress relieved outer metalized surface, in accordance with thepresent invention.

[0025]FIG. 4B illustrates the equal-potential field gradient lines inthe improved bushing of FIG. 4A.

[0026]FIG. 5 is a cross-sectional view of an improved high-voltageconnector having metalized surfaces, in accordance with the presentinvention.

[0027]FIG. 6 is an expanded view of the highly-stressed region of thehigh-voltage connector of FIG. 5.

[0028]FIGS. 7A and 7B illustrate the upper and lower layers of metalizedplastic film that are assembled, as shown in FIG. 7C, to construct animproved metalized-film capacitor.

[0029]FIG. 8 is a view of an embodiment of a rolled up axial leadmetalized-film capacitor.

[0030]FIG. 9 is a view of an embodiment of a rolled up axial leadmetalized-film, metal-foil capacitor.

DETAILED DESCRIPTION OF THE INVENTION

[0031] The present invention relates to removing the electric field fromthe internal volume of high voltage interconnects, such as bushings,connectors, and cables. The space of interest, for example, is thatbetween the center conductor and the solid dielectric insulator thatnormally provides the primary electrical insulation from the outerconductor. This invention provides a conductive surface on the insidesurface of the principal solid dielectric insulator surrounding thecenter conductor and connects the center conductor to this conductivesurface. This simple approach removes the electric field across aninherently weak region and places it in the primary insulation. Theadvantage of removing the electric fields from the weaker dielectricregion to a stronger area improves reliability, increases component lifeand operating levels, reduces noise and losses, and allows for a smallercompact design. While various techniques can be utilized to metalizedesired regions, such depend, for example, on material, size, thickness,and surface accessibility, and the simplest method uses a standardelectroless plating technique. Other known metalization techniquesinclude, but are not limited to, vapor and energetic deposition, plasmaspraying, conductive painting, and other controlled coating methods. Themetalization approach in accordance with the present invention can beeasily applied to existing high-voltage interconnect designs, and suchreceive an instant reduction of corona activity and related effects.

[0032]FIGS. 1A and 1B illustrate cross-sectional views of a generichigh-voltage bushing, 100, having a cylindrically symmetric design andgenerally used to insulate electrical conductors passing through metalwalls of protective enclosures. A generic embodiment is used to showcommon features in bushings and to illustrate the essence of thisinvention as it applies to all highly electrical-stressed structures.The bushing insulator is typically constructed of a single continuoussolid dielectric insulator material, 102, having an external (upper)section and an internal (lower) section. An external connection point,101, is the high-voltage input to or output from an arbitraryhigh-voltage device located inside an enclosure, 112. The external soliddielectric insulator, 102, provides the primary electrical insulationbetween the internal bushing conductor, 103, and the enclosure, 112. Theexternal solid dielectric insulator, 102, is typically shaped toprohibit surface flashover and provide structural support of theinternal bushing conductor, 103, of the bushing, 100. Internal bushingconductor, 103, provides the electrical connection from externalconnection point, 101, to the internal connection point, 106. Internalbushing conductor, 103, can be constructed of rigid metal or flexiblecable. The enclosure, 112, is typically at ground potential. In the caseof oil encapsulated systems, such as transformers, a metalized coating,104, on the outer surface of the lower or internal solid dielectricinsulator, 102, will extend the ground potential well inside theenclosure, 112, and below the oil fill line, 113. This metalizedcoating, 104, eliminates the triple-junction that would otherwise becreated by the internal or lower section of the solid dielectricinsulator, 102, as it penetrates the enclosure, 112, through theenclosure flange, 110, and relocates the triple point region, 114, to ahigher dielectric strength environment of oil. The upper end flange,107, and the lower end flange, 111, support the internal bushingconductor, 103, and provide a means to attach input and outputconnections. The void region, 108, extends between the solid dielectricinsulator, 102, and the internal bushing conductor, 103, constituting aregion of weaker dielectric material In current art, this weakerdielectric region becomes a troublesome source of electrical coronadischarge activity that reduces the reliability and operating level ofthe high-voltage bushing.

[0033] In the present invention, a metalized surface, 109, is applied tothe inner surface of the cylindrically shaped solid dielectricinsulator, 102. This metalized surface, 109, includes end sections whichprovide an electrical connection between the upper end flange, 107, thelower end flange, 111, the internal bushing conductor, 103, the externalconnection point, 101, and the internal connection point, 106, assuringthat they are all at the same electrical potential. In this fashion, thevoid region, 108, is completely surrounded by metallic surfaces at thesame potential, therefore no electric field can exist within the voidregion, 108, and thus there is no initiating source of electrical coronaactivity in this region. FIG. 1B shows symmetry between the externalconnection point, 101, of bushing conductor 103; the void region, 108;the metalized surface, 109; and the solid dielectric insulator, 102.

[0034]FIGS. 2A and 2B illustrate an expanded view of a bushing similarto that of FIGS. 1A-1B, showing the internal section of a high-voltagebushing, 200, below the oil-fill line, 113, without the improvementcalled out in this invention. This is representative of current art anddepicts equipotential lines developed in the void region, 204. Theinternal bushing conductor, 201, and the lower end flange, 202, areelectrically connected and provide for one of the two electrodesdefining the equipotential lines developed in the void region, 204. Theelectrically opposing electrode is extended below the oil line, 113, bya metalized outer surface, 205. Fields are distributed across the voidregion, 204, and the solid dielectric insulator, 207, as a relationshipof their discrete capacitance. The resulting equipotential linesdeveloped in the void region, 204, reach the intrinsic breakdown levelof the ambient air or oil before the intrinsic level of the soliddielectric insulator, 207, is reached. As a result, the internal sectionof the high-voltage bushing, 200, goes into electrical corona activityon the inside of the bushing opposite the triple point region, 206, oras it penetrates the enclosure, 112, opposite the enclosure flange, 110(see FIG. 1A). When the exposed insulator surface, 208, is of sufficientlength to inhibit the surface breakdown; electrical corona activity onthe inner surface of the high-voltage bushing, 203, erodes the soliddielectric insulator, 207, until the unit catastrophically fails.

[0035]FIGS. 3A and 3B illustrate the internal section of and improvedhigh-voltage bushing, 300, as an expanded view of FIG. 1A showing thebottom section of a typical high-voltage bushing, 100, below the oilfill line, 113 (see FIG. 1A). The internal bushing conductor, 301, lowerend flange, 302, and the metalized inner surface of the high-voltagebushing, 303, are electrically connected by being in direct contact andare therefore at the same electrical potential as stated in the abovedescription. The metalized outer surface, 305, of the solid dielectricinsulator, 307, defines the lower section of the high-voltage bushing,100, of FIG. 1A. The dashed lines in FIG. 3B indicate equal-potentialgradient lines and are shown to be in the stronger dielectric materialof the bushing solid dielectric insulator, 307, and not in the weakerdielectric material filling the void region, 304. The solid dielectricinsulator, 307, is considered to be made of homogenous material withoutsignificant flaws or imperfections. The metalized inner and outersurface, 303 and 305, respectively, on portions of the cylindricalhigh-voltage bushing, 303, provide controls on the shape and density ofthe electrostatic field lines within the solid dielectric insulator,307, between the two surfaces. When the metalized outer surface 305,ends at the triple region, 306, the electric fields within the soliddielectric insulator, 307, extend out into the surrounding oilenvironment, as governed by the geometric shape of the enclosure andnearby objects, as well as the relative dielectric constants. The triplepoint region, 306, will have the highest field-enhancement and is thelikely point from which electrical failure will occur. The reasonelectrical breakdown begins from this location relates directly to therapid change in the equipotential lines at the sharp edge of themetalized outer surface, 305. When the electric field stress at thetriple point region, 306, exceeds the strength of the oil environment,electrical will occur in proximity to the insulator and an arc willdevelop across the exposed insulator surface, 308, and make attachmentto the lower end flange, 302, resulting in an electrical failure thatwill likely cause permanent damage to the solid dielectric insulator,307.

[0036]FIGS. 4A and 4B show the internal section of an improvedhigh-voltage bushing, 400, previously shown in FIG. 3A. The improvementis realized by contouring the solid dielectric insulator, 407, in thevicinity of the triple point region, 306, as shown in FIG. 3A. Themetalized region of the inner surface, 403, and metalized outer surface,405, confine the radial electric field inside the solid dielectricinsulator. A gradual increase in the electric field inside the body ofthe insulator, 407, is caused as the embedded electrode, 409, reshapesthe internal fields, however, the electric field stress need not exceedthe electrical strength of the insulator material, 407. The embeddedelectrode, 409, does serve to reduce the electric field enhancement atthe triple point region, 406. As previously stated, the initiatingmechanism for breakdown depends on the field-stress at thistriple-junction and the reduced electric field provided at this point bythe contoured embedded electrode, 409, improves reliability andoperating levels. The contoured embedded electrode, 409, is designed tohave a slope of about 135 degrees with relief to the metalized outersurface, 405, to allow air bubbles that might otherwise be trapped inthe recessed portion of the embedded electrode, 409, to float up andaway from the triple point region, 406.

[0037] Several methods of metalizing dielectric surfaces are possible.The preferred method of metalizing the surfaces 109, 303, 403, and 409of the bushing insulator 102, 307, and 407 employs a strictly chemicalprocess for plating copper and copper alloys on surfaces exposed in achemical bath, also known as electroless chemical plating. Other methodsfor metalizing surfaces of ceramic dielectric materials can be employed,such as electroplating, depositing and baking metal-based inks, physicalvapor deposition, chemical vapor deposition, plasma-assisted vapordeposition and plasma spraying of metal powders in a vacuum chamber,conductive painting, and other controlled coating techniques. Othermaterial for metallic coatings can be employed, such as aluminum,nickel, silver, platinum, palladium, and gold, as well as alloysthereof. The metalized surface may have a thickness in the range ofatomic level of the material to a millimeter. The dielectric materialmay be composed of ceramics, plastics, glass, fiberglass, mica, andrubber. Also, the conductive material may be of semiconductor materials,such as cuprous oxide, germanium, gallium arsenide, gallium phosphide,indium arsenide, lead sulfide, selenium, silicon, and silicon carbide.

[0038] Another method for passing electrical current through conductivewalls of enclosures is by connectors. FIG. 5 shows a representativecoaxial connector, 500, of an improved design in a typicalconfiguration, such as a vacuum feedthrough. The outer conductive shell,501, of the connector attaches to the enclosure wall, which is typicallygrounded. The primary insulator, 502, is typically constructed of asolid dielectric material, such as plastic or ceramic. The void region,503, between the insulator, 502, and the center conductor, 504, istypically filled with gas or liquid from the ambient environment, whichis most often a weaker electrically insulating material than thestronger solid dielectric insulator, 502. A vacuum seal, 505, attachesthe center conductor, 504, to the insulator, 502. The inner surface ofthe insulator, 502, is metalized from the vacuum seal, 505, to theregion of 507. The result is that the center conductor, 504, and innersurface of adjoining dielectric, 506, are electrically connected,thereby ensuring that no electric field exists in the void region, 503,of weaker dielectric material.

[0039]FIG. 6 illustrates an expanded or enlarged view of the region 507of FIG. 5 and of controlling stress in coaxial type connectors, 600. Theouter conductive shell, 601, provides the termination of the connectorto the enclosure wall, as mentioned above. In addition, a vacuum seal isrequired between the outer conductive shell, 601, and the insulator,602. The increased thickness of the insulator, 602, adjacent to thevacuum region, 605, provides added electrical strength to this sectionof the insulator. The vacuum triple-point region, 606, defines thehighest region of stress in this vicinity. The center conductor, 603,and the inner surface region of metalization, 604, as mentioned above,are electrically connected, and, as such, remove the electrical fieldsin the weaker ambient region, 609. Metalizing the inner surface, 604, ofinsulator, 602, as shown, also removes the electrical fields from thedielectric support 608. Properly ending the metalization 604, definesthe ambient atmosphere triple-point region 607. The atmospheretriple-point region 607, represents the significant electrical fieldenhancement in this connector.

[0040] Typical connectors use plastics as the principal dielectricmaterial. Some vacuum feedthrough connectors will use ceramics as aninsulator to be more compatible with the vacuum environment. Connectorsusing ceramics can easily use the same metalization process as describedfor high-voltage bushings. Plastics can be more challenging in qualityplating. Platable acrylonitrile-butadiene-styrene (ABS) plastic has beenshown to be a very useful dielectric. Another widely used plastic forconnectors is Teflon (polytetrafluorethylene), presently requiringenergetic deposition techniques. One possible lay down process forconductive surfaces on Teflon is by controlled explosive copper wiretechniques.

[0041] Another area for application of the present invention forimproving performance of highly stressed electrical insulationstructures includes improvement to metalized film and metalizedfilm/foil capacitors. Multilayer film capacitors have several differentconstruction techniques. Common to all current art capacitor structuresinvolves alternating layers of conductive and nonconductive dielectricmaterial. FIGS. 7A, 7B, and 7C illustrate cut-away views of a metalizedfilm capacitor using the disclosed improved manufacturing technique.FIGS. 7A and 7B show a cross-section of the first and second metalizeddielectric film, 700 and 706. The dielectric films 701 and 707 arecontinuous high-quality film material of homogenous material. Themetalization process involves a quality conductive surface applied toboth sides of the dielectric film with a masked region on opposite andopposing sides to provide nonconductive regions 710. The top layer ofthe first dielectric film 701 extends to a summing electrode for thepositive electrode 703. In contrast, the bottom metalized layer 709 ofthe second dielectric film 707 extends to the same summing electrode forthe positive electrode 703. The opposing electrodes, defined as thelower metalization 704 of the first metalized dielectric film 701 andthe upper metalization 708 of the second dielectric 707, both extend tothe summing electrode for the negative electrode 705. A detail to themanufacturing process is that the tape defining each of these metalizedfilm/foils is the same, and in the roll-up process one of the tapes isturned over so that the metaled surfaces of the two adjacent metalizedsurfaces are in the same direction. The effect of this is illustrated inFIG. 7C by placing the first, 701, and second, 707, dielectric films inclose proximity to each other. The void region, 711, typical to theabove-mentioned regions, represents the weak area of dielectricmaterial. During the roll-up assembly process the adjacent metalizedsurfaces make electrical contact by physical pressure and remove theelectrical field across this weak void region 711. The current art forthis type of capacitor is to have metal on one side of the dielectricwith alternating extension of the electrode to define the capacitorelectrodes. In contrast to this invention, the effect of the current artassembly process traps weaker dielectric material without a removalmechanism, as shown in FIG. 7C. As part of this invention, the processof eliminating weak electrical regions of stress is obtained by havingmetalized surfaces surrounding these regions of concern.

[0042]FIG. 8 illustrates an example of a rolled up construction of anaxial lead metalized film capacitor. Metalized surface, 801, ondielectric film, 804, and metalized surface, 802, on dielectric film,803, are rolled adjacent to each other providing one of the capacitorelectrodes. This process has removed electric fields that would normallybe in this region and increases the reliability and operating levels.Similarly, metalized surface, 807, on dielectric film, 804, andmetalized surface 808, on dielectric film 803, provide the othercapacitor electrode. Similar connection to each of the extendedelectrodes is made with a conductive disk, 809. Surface areas, 805 and806, provide insulation between the two electrodes defining thecapacitor.

[0043]FIG. 9 shows the inclusion of a metal foil, 901 and 902, rolledbetween the two otherwise adjacent metalized surfaces. The purpose ofthe foil provides a lower internal resistance, allows ease of electrodeextension over the edge of the dielectric film, and allows high-currentoperations.

[0044] The optimum metalization technique for the FIGS. 8 and 9application is vapor deposition with controlled masking in desiredareas. The process can be done on both sides during a single pass or ona single side in a double pass.

[0045] It has thus been shown that the present invention enables theremoval of electric field in weak areas of high-voltage interconnects,such as bushing, connectors, cables, capacitors, etc. In contrast toprior attempts to remove electric fields in weak regions, the inventionprovides a conductive surface on the inside surface of the principalsolid dielectric insulator surrounding the center conductor and connectsthe center conductor to this conductive surface.

[0046] The use of this invention in manufacturing and field managementapplies to all high-voltage interconnects. In addition to improved lifeof existing high-voltage interconnects, a reduction of corona inducednoise is anticipated. Some of the immediate applications include:accelerators, high-voltage bushings in power supplies, high-voltageconnectors, compact high-voltage sources, and highly-reliablehigh-voltage structures. The use of this invention will improveequipment life expectancy, provide added compactness for the sameoperating levels, lighten the environmental impact from alternativefield management controls, and improve the electromagnetic capability ofequipment Uses include power grid components, such as transformers,feed-through bushings and switch gear, high-voltage power supplies,modulators, high-voltage capacitors and tubes, and space-basedcommunication systems.

[0047] While particular embodiments, materials, parameters, etc., havebeen described and/or illustrated to exemplify and teach the principlesof the invention, such are not intended to be limiting. Modificationsand changes may become apparent to those skilled in the art, and it isintended that the invention be limited only by the scope of the appendedclaims.

The invention claimed is:
 1. A method for removing an electric fieldfrom any dielectric/metal interface of high-voltage interconnects,comprising: providing an interconnect having at least one electrode anda solid dielectric insulator surrounding the electrode, and providing aconductive surface on an inside surface of the solid dielectricinsulator.
 2. The method of claim 1, wherein providing the conductivesurface is carried out by depositing conductive material on the insidesurface of the solid dielectric insulator to a thickness of aboutangstroms to one millimeter.
 3. The method of claim 1, wherein providingthe conductive surface is carried out by depositing conductive materialby a technique selected from the group consisting of electroplating,electroless chemical plating, depositing and baking metal-based inks,physical vapor deposition, chemical vapor deposition, plasma-assistedvapor deposition, plasma spraying of metal powers, conductive painting,and other controlled coating techniques.
 4. The method of claim 3,wherein the conductive material is selected from the group consisting ofcopper, copper alloys, aluminum, palladium, nickel, silver, platinum,gold, and alloys thereof, cuprous oxide, germanium, gallium, arsenide,gallium phosphide, indium arsenide, lead sulfide, selenium, silicon, andsilicon carbide.
 5. The method of claim 3, wherein said solid dielectricinsulator is formed from the group consisting of ceramics, plastics,glass, fiberglass, mica, and rubber.
 6. In a high-voltage structurehaving a first electrode surrounded by air or vacuum, a bulk insulatorsurrounded by air or vacuum, and another electrode at a differentpotential, the improvement comprising: means for removing an electricfield across a weak region and placing it in the bulk insulation, saidmeans comprising a conductive surface on an inside surface of the bulkinsulator.
 7. The high-voltage structure of claim 6, selected from thegroup consisting of bushings, connectors, coaxial connectors, film/foilcapacitors, and cables.
 8. The high-voltage structure of claim 6,wherein said conductive surface is composed of material selected fromthe group consisting of copper, copper alloys, aluminum, nickel, silver,platinum, palladium, gold, and alloys thereof.
 9. The high-voltagestructure of claim 6, wherein said bulk insulator is composed ofdielectric materials selected from the group consisting of ceramics,plastics, glass, fiberglass, mica, and rubber.
 10. The high-voltagestructure of claim 6, wherein said conductive surface is composed ofsemiconductor materials selected from the group consisting of cuprousoxide, germanium, gallium arsenide, gallium phosphide, indium arsenide,lead sulfide, selenium, silicon, and silicon carbide.
 11. Thehigh-voltage structure of claim 6, wherein said conductive surface isformed after fabrication of the structure.
 12. In a high-voltageinterconnect having two electrodes of different potentials with twodifferent dielectric materials separating the electrodes, theimprovement comprising: means for removing the electric field across theweaker of the two dielectric materials and placing the electric field inthe stronger of the two dielectric materials.
 13. The improvement ofclaim 12, wherein said means comprises a conductive surface on a surfaceof the stronger of the two dielectric materials.
 14. The improvement ofclaim 12, wherein said stronger of the two dielectric materials iscomposed of ceramic dielectric materials.
 15. The improvement of claim13, wherein said conductive surface has a thickness in the range fromangstroms to one millimeter.
 16. The improvement of claim 13, whereinsaid conductive surface composed of material selected from the groupconsisting of copper, copper alloys, aluminum, nickel, silver, and gold.17. The high voltage interconnect of claim 13, selected from the groupconsisting of bushings, connectors, cables, and multilayer capacitors.18. The high voltage interconnect of claim 17, wherein said interconnectconsists of a multilayer capacitor of a metalized film/foil type. 19.The high voltage interconnect of claim 17, wherein said interconnectconsists of a coaxial connector.
 20. The high-voltage interconnect ofclaim 17, wherein said interconnect consists of bushings having asingle, continuous solid dielectric material spaced from a centralelectrode.
 21. A method for improving performance of highly stressedelectrical insulating structures, such as found in high-voltagebushings, connectors, and capacitors, by providing a conductive surfaceon a solid dielectric insulating material wherever it is to be directlyadjacent to, or in direct contact with, an adjoining metal electrode,and providing an interconnect at one or more places between theadjoining metal electrode and the conductive surface of the soliddielectric insulator by direct contact or some other means, therebyeliminating the electric field that would otherwise exist in the gapbetween the solid dielectric insulator and the adjoining metalelectrode, thus avoiding electrical breakdown of any weaker dielectric,typically gas or liquid, that might reside in the gap or void regionbetween the is solid dielectric insulator and the adjoining metalelectrode.
 22. The method of claim 21, wherein the solid dielectricinsulating structure is formed from material selected from the group ofceramics, plastics, glass, fiberglass, mica, and rubber.
 23. The methodof claim 21, wherein the conductive surface is formed by depositing onthe insulator structure by a technique selected from the groupconsisting of electroplating, electroless chemical plating, depositingand baking metal-based inks, physical vapor deposition, chemical vapordeposition, plasma-assisted vapor deposition, plasma spraying of metalpowders, conductive painting, and other controlled coating techniques.24. The method of claim 23, wherein the conductive material is formedfrom material selected from the group of metallic elements includingaluminum, copper, gold, indium, lead, nickel, palladium, platinum,silver, tin, zinc, and their alloys.
 25. The method of claim 23, whereinthe conductive material is formed from material selected from the groupof semiconductor materials, including cuprous oxide, germanium, galliumarsenide, gallium phosphide, indium arsenide, lead sulfide, selenium,silicon, and silicon carbide.
 26. An electrical feedthrough, or bushing,having a solid dielectric insulator between the center conductingelectrode and the outer conducting flange, housing, or enclosure,wherein a conductive surface is provided on the solid dielectricinsulator wherever it is to be directly adjacent to, or in directcontact with, the center conducting electrode, and wherein theconductive surface on the solid dielectric insulator is electricallyconnected to the center conductor or its supporting conducting flangesby direct contact or some other means, thereby eliminating the electricfield that would otherwise exist in the gap between the centerconducting electrode and the solid dielectric insulator, thus avoidingelectrical breakdown of any weaker dielectric, typically gas or liquid,that might reside in the gap or void region between the centerconducting electrode and the solid dielectric insulator.
 27. Theelectrical feedthrough or bushing of claim 26, wherein a conductivesurface is also provided on the outer portion of the solid dielectricinsulator from the vicinity of the flange that attaches to the wall ofthe enclosure, and extending inward some distance within the enclosureand away from the wall, and whereby the solid dielectric material has anindented contoured shape, also with a metalized surface, that serves toconcentrate the electric fields inside the stronger solid dielectricmaterial and reduce the electric field concentration in the vicinity ofthe so-called triple-point region where the conductive surface ends, andthe three dissimilar materials (solid-dielectric, metallic coating, andother dielectric contained within the enclosure) all meet.
 28. Acoaxial-type electrical connector having a solid dielectric insulatorbetween the center conductor and the outer conductive shell, wherein aconductive surface is provided on the solid dielectric insulatorwherever it is to be directly adjacent to, or in direct contact with,the center conductor, and wherein the conductive surface on the soliddielectric insulator is electrically connected to the center conductoror its supporting conducting flanges by direct contact or some othermeans, thereby eliminating the electric field that would otherwise existin the gap between the center conductor and the solid dielectricinsulator, thus avoiding electrical breakdown of any weaker dielectric,typically gas or liquid, that might reside in the gap or void regionbetween the center conductor and the solid dielectric insulator.
 29. Thecoaxial connector of claim 28, in a configuration to provide a vacuum orpressure seal, as well as to pass electrical current, and having a soliddielectric insulator between the center conductor and the outerconductive shell, and wherein the thickness of the solid dielectricinsulator is increased in the vicinity of the triple-point region on thevacuum or low-pressure side of the connector, and wherein the thicknessof the solid dielectric insulator is tapered in the region where adielectric support is provided between the center conductor and theinner surface of the solid dielectric insulator, and wherein aconductive surface is provided on the solid dielectric insulatorwherever it is to be directly adjacent to, or in direct contact with,the center conductor, and particularly in the tapered region where thedielectric support is provided, thereby eliminating the electric fieldthat would otherwise exist in the gap between the center conductor andthe solid dielectric insulator, particularly in the triple-point regionswhere the vacuum or pressure seal is made, thus avoiding electricalbreakdown of any weaker dielectric, typically vacuum or gas, that mightreside in the gap or void region between the center conductor and thesolid dielectric insulator.
 30. A dielectric film capacitor constructedof two or more layers of dielectric films that are each metalized onboth sides, rather than only on one side, whereby the bottom metalizedsurface of the top dielectric film layer and the top metalized surfaceof the bottom dielectric film layer are connected at one common edgeelectrode, so that said surfaces of said dielectric films are at thesame electrical potential, thereby eliminating the electric field thatcould otherwise exist in the gap or void region between the surface of abare dielectric film and the surface of an adjacent metalized dielectricfilm, thus avoiding electrical breakdown of any weaker dielectric,typically gas or liquid, that might reside in the gap or void regionbetween the adjacent layers of dielectric films that comprise thecapacitor.